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Abstract:

A power semiconductor module is disclosed, including a plate-type
substrate fitted with at least one component, and a base plate provided
for dissipating heat from the component via the substrate. In at least
one embodiment, a supporting apparatus, which keeps the substrate in
thermal contact with the base plate, has a central pressure bolt adjoined
by a plurality of stamps which extend in different directions and are
intended to contact-connect the substrate, the individual stamps being at
non-uniform distances from the substrate in the mechanically unloaded
state of the pressure bolt.

Claims:

1. A power semiconductor module, comprising:a plate-type substrate fitted
with at least one component;a base plate to dissipate heat from the
component via the substrate; anda supporting apparatus to keep the
substrate in thermal contact with the base plate, the supporting
apparatus including elastic properties including a central pressure bolt
adjoined by a plurality of stamps which extend in different directions
and are intended to contact-connect the substrate, the individual stamps
being at non-uniform distances from the substrate in a mechanically
unloaded state of the pressure bolt, and the supporting apparatus
including a central stamp situated in an extension of the pressure bolt
and a plurality of lateral stamps extending orthogonal to the pressure
bolt and elastically connected to the pressure bolt in a resilient
manner, at least the lateral stamps including a V-shaped cross section,
and an edge of the stamp being intended to rest on the substrate.

2. The power semiconductor module as claimed in claim 1, wherein the
central stamp is integrally produced with the pressure bolt and with the
lateral stamps from plastic.

3. The power semiconductor module as claimed in claim 2, wherein the
central stamp is at a greater distance from the substrate than the
lateral stamps in the mechanically unloaded state of the pressure bolt.

4. The power semiconductor module as claimed in claim 3, wherein the
lateral stamps are at an increasingly greater distance from the substrate
toward the central stamp in the mechanically unloaded state of pressure
bolt.

5. The power semiconductor module as claimed in claim 1, wherein the
substrate is in the form of a direct copper bonding substrate.

6. The power semiconductor module as claimed in claim 1, wherein the
pressure bolt is supported on a busbar on a side opposite the stamps.

7. The power semiconductor module as claimed in claim 6, wherein the
busbar is fastened to a housing which holds at least one component and is
open on a side on which the busbar is arranged.

8. The power semiconductor module as claimed in claim 2, wherein the
substrate is in the form of a direct copper bonding substrate.

9. The power semiconductor module as claimed in claim 2, wherein the
pressure bolt is supported on a busbar on a side opposite the stamps.

10. The power semiconductor module as claimed in claim 9, wherein the
busbar is fastened to a housing which holds at least one component and is
open on a side on which the busbar is arranged.

11. The power semiconductor module as claimed in claim 3, wherein the
substrate is in the form of a direct copper bonding substrate.

12. The power semiconductor module as claimed in claim 3, wherein the
pressure bolt is supported on a busbar on a side opposite the stamps.

13. The power semiconductor module as claimed in claim 12, wherein the
busbar is fastened to a housing which holds at least one component and is
open on a side on which the busbar is arranged.

14. The power semiconductor module as claimed in claim 4, wherein the
substrate is in the form of a direct copper bonding substrate.

15. The power semiconductor module as claimed in claim 4, wherein the
pressure bolt is supported on a busbar on a side opposite the stamps.

16. The power semiconductor module as claimed in claim 15, wherein the
busbar is fastened to a housing which holds at least one component and is
open on a side on which the busbar is arranged.

17. The power semiconductor module as claimed in claim 5, wherein the
pressure bolt is supported on a busbar on a side opposite the stamps.

18. The power semiconductor module as claimed in claim 17, wherein the
busbar is fastened to a housing which holds at least one component and is
open on a side on which the busbar is arranged.

19. A power semiconductor module, comprising:a plate-type substrate fitted
with at least one component;a base plate to dissipate heat from the
component via the substrate; anda supporting apparatus, thermally
contacting the substrate and the base plate, including a central pressure
bolt, adjoined by a plurality of stamps which extend in different
directions, to contact-connect the substrate, the individual stamps being
at non-uniform distances from the substrate in a mechanically unloaded
state of the pressure bolt.

20. The power semiconductor module as claimed in claim 19, wherein the
central stamp is integrally produced with the pressure bolt and with the
lateral stamps from plastic.

[0002]Embodiments of the invention generally relate to a power
semiconductor module. For example, the may relate to one including a
substrate which is fitted with at least one component and is kept in
thermal contact with a cooling element by way of a supporting apparatus.

BACKGROUND

[0003]DE 33 23 246 A1 discloses a power semiconductor module having a
metal base plate as the cooling element, which base plate is adhesively
bonded to a substrate, namely a ceramic plate which has been metallized
on both sides, with the aid of an elastic adhesive thermally conductive
paste. A plastic housing of the power semiconductor module has struts
with supports which are intended to counteract deformation of the
substrate. However, the struts and supports require a considerable amount
of installation space which is thus no longer available for fitting
components to the substrate.

[0004]A power semiconductor module which is disclosed in DE 35 08 456 C2
likewise has struts which mechanically interact with a ceramic substrate.
Threaded holes for screwing in adjusting screws are provided in the
struts. The adjusting screws press on intermediate pieces which are made
of plastic, for example glass-fiber-reinforced thermosetting plastic, and
are adhesively bonded to the substrate or to a component. An intermediate
piece arranged on a thyristor or a circular copper blank has a slot for
passing a connecting clip through to the thyristor gate.

[0005]A further power semiconductor module which is disclosed in EP 1 083
503 B1 has a base plate which is suitable for dissipating heat and has a
substrate, which is fitted with power semiconductor chips, arranged on
it, said substrate being able to be pressed onto the base plate using
pressure elements. The pressure elements have conductive connecting
elements which are arranged between the substrate and contact rails and
are in the form of contact cords which have an elastic core and an
electrically conductive sheath. The contact cords require a considerable
amount of free space on the substrate.

SUMMARY

[0006]In at least one embodiment, the invention specifies a power
semiconductor module in which a substrate which is fitted with a
heat-generating component is connected to a cooling element in a
particularly space-saving and installation-friendly manner.

[0007]According to an embodiment of the invention, a power semiconductor
module has a plate-type substrate, in particular a direct copper bonding
(DCB) substrate, which is fitted with at least one component, as well as
a base plate which is provided for the purpose of dissipating heat from
the component via the substrate. In this case, a base plate is understood
as meaning any part which dissipates heat and has a surface on which the
substrate rests directly or indirectly, for example using a thermally
conductive paste. A supporting apparatus is designed to keep the
substrate in thermal contact with the base plate. This supporting
apparatus is elastic and comprises a central pressure bolt which extends
normal to the substrate and is adjoined by a plurality of stamps which
extend in different directions and are intended to contact-connect the
substrate, the individual stamps being at non-uniform distances from the
substrate surface in the mechanically unloaded state of the pressure
bolt.

[0008]The stamps, in at least one embodiment, comprise a central stamp
which is identical to, or aligned with, the pressure bolt as well as at
least two lateral stamps which extend essentially orthogonal to the
pressure bolt, are elastic per se and/or are connected to the pressure
bolt in an elastically resilient manner. The last-mentioned stamps may be
arranged in a rotationally symmetrical manner with respect to a
geometrical axis described by the pressure bolt. In the case of only two
lateral stamps, the supporting apparatus may be distinguished by a very
narrow design overall, whereas more extensive support can be achieved
with a larger number of stamps. In all cases, when the power
semiconductor module is ready for operation, the pressure bolt is loaded
with a force, which acts on the substrate in a perpendicular direction,
in such a manner that all of the stamps transfer a force between the
pressure bolt and the substrate.

[0009]The central stamp and the lateral stamps can be integrally produced
with the pressure bolt, for example in a plastic injection-molding
method. If a housing of the power semiconductor module is likewise
fabricated from plastic, it is also possible to integrally form the
entire supporting apparatus with the housing or a housing part, for
example a housing cover.

[0010]The force with which the supporting apparatus presses onto the flat
substrate can preferably be set, for example using a setting screw.
Additionally or alternatively, the supporting apparatus can be
elastically mounted on the side facing away from the substrate. A leaf
spring or a rail which is elastic at least to a slight extent is suitable
for this purpose, for example.

[0011]According to one example refinement, a plurality of lateral stamps
of the supporting apparatus are arranged in the mechanically unloaded
state of the latter, that is to say without the action of force when the
supporting apparatus rests on the substrate, in such a manner that only
those regions of the lateral stamps--a respective single point in the
extreme theoretical case--which are furthest away from the axis of the
supporting apparatus, that is to say from the axis of symmetry of the
pressure bolt, come into abutment against the substrate. The distance
between the substrate and the individual lateral stamps (also referred to
as legs) increases toward said axis. Expressed in simplified terms, this
means that the legs of the supporting apparatus are placed such that they
are at least slightly oblique with respect to the surface of the
substrate. The same also applies in cases in which the supporting
apparatus is not supported on the substrate directly but rather on a
component, for example.

[0012]In a different respect, an embodiment in which at least the lateral
stamps, preferably all stamps, have a V-shaped cross section is
advantageous, only one edge of each stamp being intended to rest on the
substrate. The narrow, virtually linear contact regions between the
substrate and the stamps of the supporting apparatus mean that
particularly good use is made of the elastic material properties of the
preferably integral supporting apparatus. The cross section of the stamps
which widens with increasing distance from the substrate also makes it
possible to apply a relatively large force to the substrate in the case
of a supporting apparatus which is fabricated from plastic. At the same
time, the supporting apparatus can be integrated in the power
semiconductor module in a space-saving manner. Overall, taking into
account the elastic material properties of the stamps, in particular, the
supporting apparatus can be configured in such a manner that, during
operation of the power semiconductor module, all stamps load the
substrate with a pressure which is uniform both inside each individual
stamp and, in contrast, between the stamps.

[0013]The supporting apparatus is preferably in the form of an
electrically insulating component overall. Plastics are particularly
suitable for producing the supporting apparatus in this aspect too. If
electrical conductivity of the supporting apparatus is required in the
individual case, this can be produced, for example, from a polymer
material with a metal sheath.

[0014]The power semiconductor module is a motor soft starter, for example.
Semiconductor relays or semiconductor contactors can likewise be
implemented as power semiconductor modules according to an embodiment of
the invention. An advantage of an embodiment of the invention is, in
particular, that a supporting apparatus having elastically resilient
stamps which taper toward a flat substrate makes it possible to apply
force in a particularly uniform manner and at the same time requires only
a small amount of area on the substrate which is otherwise intended to be
fitted with power semiconductors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]One example embodiment of the invention is explained in more detail
below using drawings, in which:

[0016]FIG. 1 shows a perspective view of a power semiconductor module
having a supporting apparatus,

[0017]FIG. 2 shows the supporting apparatus of the power semiconductor
module according to FIG. 1,

[0018]FIG. 3 shows a sectional illustration of the power semiconductor
module with a supporting apparatus which is not completely pressed onto a
substrate, and

[0019]FIG. 4 shows, in an illustration similar to FIG. 3, the power
semiconductor module with a supporting apparatus which rests completely
on the substrate.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0020]The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the
present invention. As used herein, the singular forms "a", "an", and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood that
the terms "includes" and/or "including", when used in this specification,
specify the presence of stated features, integers, steps, operations,
elements, and/or components, but do not preclude the presence or addition
of one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.

[0021]Spatially relative terms, such as "beneath", "below", "lower",
"above", "upper", and the like, may be used herein for ease of
description to describe one element or feature's relationship to another
element(s) or feature(s) as illustrated in the figures. It will be
understood that the spatially relative terms are intended to encompass
different orientations of the device in use or operation in addition to
the orientation depicted in the figures. For example, if the device in
the figures is turned over, elements described as "below" or "beneath"
other elements or features would then be oriented "above" the other
elements or features. Thus, term such as "below" can encompass both an
orientation of above and below. The device may be otherwise oriented
(rotated 90 degrees or at other orientations) and the spatially relative
descriptors used herein are interpreted accordingly.

[0022]Although the terms first, second, etc. may be used herein to
describe various elements, components, regions, layers and/or sections,
it should be understood that these elements, components, regions, layers
and/or sections should not be limited by these terms. These terms are
used only to distinguish one element, component, region, layer, or
section from another region, layer, or section. Thus, a first element,
component, region, layer, or section discussed below could be termed a
second element, component, region, layer, or section without departing
from the teachings of the present invention.

[0023]In describing example embodiments illustrated in the drawings,
specific terminology is employed for the sake of clarity. However, the
disclosure of this patent specification is not intended to be limited to
the specific terminology so selected and it is to be understood that each
specific element includes all technical equivalents that operate in a
similar manner.

[0024]Referencing the drawings, wherein like reference numerals designate
identical or corresponding parts throughout the several views, example
embodiments of the present patent application are hereafter described.
Like numbers refer to like elements throughout. As used herein, the terms
"and/or" and "at least one of" include any and all combinations of one or
more of the associated listed items.

[0025]FIGS. 1 and 3 and 4 show different views of a power semiconductor
module 1 comprising a plurality of components 3, namely power
semiconductor components, which are arranged in a housing 2. The
individual components 3 are situated on a plate-type substrate 4 which is
in the form of a direct copper bonding (DCB) substrate. In the case of
such a DCB substrate, a copper foil is applied to both sides of a ceramic
plate in a direct bonding method. Situated under the substrate 4, that is
to say on that side of the substrate 4 which is opposite the components
3, is a base plate 5 which is illustrated only by way of indication in
FIG. 3, is fabricated from light metal, for example, and acts as a
cooling element which dissipates heat generated in the components 3 via
the substrate 4. The base plate 5 can be connected to cooling ribs in a
manner which is not illustrated or can be integrally formed with such
cooling ribs. The base plate 5 may also be a cooler through which a
liquid medium flows or may be a component which is thermally conductively
connected to such a cooler.

[0026]In order to reliably keep the substrate 4 in thermal contact with
the base plate 5, a supporting apparatus 6 is braced between a busbar 7
which runs on the top side of the housing 2, that is to say is arranged
on that side of the housing 2 which is opposite the cooling element 5,
and the substrate 4. Apart from the busbar 7, the top side of the housing
2 is open. The supporting apparatus 6 is produced as a plastic part, for
example in an injection-molding method, and has a central pressure bolt 8
which is oriented normal to the substrate 4 and to the base plate 5, is
supported on the busbar 7 and is adjoined by a total of five stamps 9, 10
which rest on the substrate 4. The stamps 9, 10 which are integrally
formed with the pressure bolt 8 comprise a central stamp 9, which is
situated in a straight extension of the pressure bolt 8, and four lateral
stamps 10 which extend essentially orthogonal to the pressure bolt 8 in
the form of a star.

[0027]FIG. 3 shows the installation situation of the supporting apparatus
6 in the housing 2 when the pressure bolt 8 has not yet been mechanically
loaded. In this case, only corner points 11 at the outer ends of the
lateral stamps 10 rest on the substrate 4. In contrast, the central stamp
9 is completely raised from the substrate 4. As is evident from FIG. 2,
in particular, each of the stamps 9, 10--also referred to as legs of the
supporting apparatus 6--has a V-shaped cross section, only edges 12, 13
of the lateral stamps 10 or of the central stamp 9 being intended to rest
on the substrate 4. Instead of pressing onto the substrate 4 directly, in
embodiments which are not illustrated, the stamps 9, 10 may also press
onto the substrate using intermediate pieces which are arranged on the
substrate 4 or on components 3, as disclosed, in principle, in DE 35 08
456 C2, for example. In such a case, the distances between the stamps 9,
10 and the intermediate pieces, which act as force-transmitting elements,
rather than the distances between the stamps 9, 10 and the substrate 4
are decisive for the method of operation of the supporting apparatus 6.

[0028]Each of the lateral stamps 10 is, on the one hand, at least slightly
elastic per se and is, on the other hand, elastically connected to the
pressure bolt 8 which is intended to be loaded with a force F.
Reinforcing structures 14 which respectively connect two lateral stamps
10 to one another are formed in the region in which the lateral stamps 10
adjoin the pressure bolt 8. The elastic properties of the supporting
apparatus 6 can be easily adapted to the boundary conditions existing in
the individual case, for example the mechanical properties of the
substrate 4, by varying these reinforcing structures 14, in particular.
For the purpose of mechanical stabilization, the surface of the pressure
bolt 8 has ribs 15 which run in the axial direction, that is to say in
the direction of the force F.

[0029]If the pressure bolt 8 is loaded with a force in the direction of
the base plate 5, for example using an adjusting screw which is not
illustrated and is screwed into the busbar 7, the four lateral stamps 10
which are arranged in a symmetrical manner with respect to the pressure
bolt 8 and are elastically articulated to the latter change from the
positioning illustrated in FIG. 3 to the end position illustrated in FIG.
4 which shows the arrangement during intended operation of the power
semiconductor module 1. In this case, the edges 12 of the lateral stamps
10 and the edge 13 of the central stamp 9 rest completely on the
substrate 4 with a uniform application of pressure. Despite the narrow
design of the edges 12, 13, the supporting apparatus 6 thus introduces
force into the substrate over a relatively large area. At the same time,
on account of the V shape of the stamps 9, 10, the supporting apparatus 6
takes up only a small amount of area on the substrate 4 which has been
fitted with the components 3.

[0030]Further, elements and/or features of different example embodiments
may be combined with each other and/or substituted for each other within
the scope of this disclosure and appended claims.

[0031]Example embodiments being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the present
invention, and all such modifications as would be obvious to one skilled
in the art are intended to be included within the scope of the following
claims.